[docs] [issue29866] Added datetime_diff to datetime.py.

[Decorater]

Decorater added the comment:

Alright I revised it a bit locally too

>>> import datetime
>>> datetime.datetime_diff(datetime.datetime(2017, 1, 31), datetime.datetime(2017, 1, 31))
''
>>> datetime.datetime_diff(datetime.datetime(2016, 12, 31, 23, 59, 59), datetime.datetime(2017, 1, 1))
'1 year ago.'
>>> datetime.datetime_diff(datetime.datetime(2016, 1, 31), datetime.datetime(2017, 1, 31, 1))
'1 year, 1 hour ago.'
>>>

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29866>
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